The indoor radon and thoron variability with building materials, season, and tropical region are important, while calculating the inhalation dose. In present work, the results of indoor radon and thoron concentration carried out by pin-hole based dosimeters in five well-populated districts of Haryana, India are reported. The results showed that the indoor radon and thoron concentration varied from 10 to 82 Bq/m3 and 7 to 180 Bq/m3, respectively. The variability of indoor thoron concentration in different seasons has random trends due to different ventilation and short half-life. The radon concentration in the dwellings was lower than the limits (100 Bq/m3) recommended by World Health Organization and worldwide average (40 Bq/m3). The first results of indoor radon and thoron by pinhole based radon/thoron discriminating dosimeter in this study area are presented.